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testis

testis

[tes-tis]
testis or testicle, one of a pair of glands that produce the male reproductive cells, or sperm. In fetal life the testes develop in the abdomen, then descend into an external sac, the scrotum. A testis is composed of about 800 coiled seminiferous tubules whose linings contain cells that develop into sperm. These tubules merge into a larger tube called the epididymis that leads out of the testis into the vas deferens. Between the seminiferous tubules there is interstitial tissue that secretes the male sex hormone testosterone, which stimulates the development of the male reproductive system and secondary sex characteristics. Sometimes the testes do not descend normally before or shortly after birth and remain in the abdomen or groin. Such a condition requires medical attention or the gland will eventually become sterile. See also reproductive system.
or testicles

Male reproductive organs (see reproductive system). Humans have two oval-shaped testes 1.5–2 in. (4–5 cm) long that produce sperm and androgens (mainly testosterone), contained in a sac (scrotum) behind the penis. Each testis is divided into 200–400 lobes containing three to 10 very thin coiled tubes (seminiferous tubules) each, which produce the sperm and contract to expel them through a complex network of canals to another structure in the scrotum, the epididymis, for temporary storage. The cells in the testes are undeveloped in early childhood; at puberty they are stimulated by hormones to develop into fertile sperm cells.

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